[Frontiers in Bioscience 14, 2747-2756, January 1, 2009]

Tollip attenuated the hypertrophic response of cardiomyocytes induced by IL-1beta

Yulong Hu1,2, Ting Li1, Yongmei Wang1, Jing Li1, Lin Guo1, Meiling Wu1, Xiaohong Shan1, Lingli Que1, Tuanzhu Ha3, Qi Chen1, Jim Kelley4, Yuehua Li1

1Department of Pathophysiology, Nanjing Medical University, Nanjing, 210029, China, 2Department of Physiology, Xiangnan University, Chenzhou, 423043, China, 3Department of Surgery, East Tennessee State University, Johnson City, TN 37614, 4Department of Internal Medicine, East Tennessee State University, Johnson City, TN 37614

TABLE OF CONTENTS

1. Abstract
2. Introduction
3. Materials and Methods
3.1. Experimental animals
3.2. Induction of cardiac hypertrophy by transverse aortic constriction (TAC)
3.3. Echocardiography
3.4. Cell culture and pCMV-Tollip plasmid transfection
3.5. Image analysis of cardiomyocytes
3.6. Western blot analysis
3.7. Immunoprecipitation (IP)
3.8. RT-PCR assay
3.9. Electrophoretic mobility shift assay (EMSA) 3.10. Statistical analysis
4. Results
4.1. TAC induced cardiac hypertrophy
4.2. TAC reduced the association of IRAK with Tollip in the myocardium
4.3. TAC increased NF-kappaB binding activity and p38 phosphorylation in the myocardium
4.4. Overexpression of Tollip attenuated the IL-1beta-stimulated hypertrophic response of neonatal cardiac myocytes
4.5. Overexpression of Tollip prevented the dissociation of Tollip from IRAK-1 following IL-1beta stimulation
4.6. Overexpression of Tollip attenuated IL-1beta-increased NF-kappaB binding activity and p38 phosphorylation
5. Discussion
6. Acknowledgement
7. References

1. ABSTRACT

We examined the role of Tollip in the hypertrophic response of cardiomyocytes. C57BL/6 mice were subjected to transverse aortic constriction (TAC) for 2 weeks and age-matched sham surgical operated mice served as control. TAC significantly reduced the association of Tollip with IRAK-1 by 66.4 percent and increased NF-kappaB binding activity by 86.5 percent and the levels of phospho-p38 by 114.6 percent in the myocardium compared with sham control, respectively. In vitro experiments showed that IL-1beta stimulation also significantly reduced the association of Tollip with IRAK-1 and increased NF-kappaB binding activity in neonatal cardiomyocytes. Tollip overexpression by transfection of cardiac myocytes significantly attenuated the IL-1beta-induced hypertrophic response of cardiac myocytes as evidenced by reduced cell size (16.4 percent) and decreased ANP expression (33.3 percent). Overexpression of Tollip also reduced NF-kappaB binding activity by 30.7 percent and phospho-p38 by 47.1 percent, respectively. The results suggest that Tollip could be a negative regulator during the development of cardiac hypertrophy. The negative regulation of cardiac hypertrophy by Tollip may involve downregulation of the MyD88-dependent NF-kappaB activation pathway.